Electric Dipole Absorption Research Articles

Dielectric permittivity of organosilicate glass thin films on a sapphire substrate determined using time-domain THz and Fourier IR spectroscopy

The engineering of dielectrics such that they have low dielectric constants is an important challenge in the semiconductor industry. The IR absorption and THz relaxation make a significant contribution to the low-frequency dielectric constant of porous organosilicate glass (OSG) thin films used in the interconnects of integrated circuits as low-k dielectrics. Determination of the dielectric contributions with the aid of the electric dipole absorption bands in the THz region has certain methodological limitations owing to the effect of the substrate. To overcome this problem, we used a c-cut sapphire plate as a substrate, which is optically isotropic and transparent in the THz range. The parameters of both the IR and THz absorption bands in the OSG films were measured using Fourier IR and pulsed THz spectroscopy and analysed using the classical oscillator model. The contribution of the THz relaxation is responsible for approximately 15%–17% of the value of the low-frequency dielectric constant.

Evaluate the potential utilization of B24N24 fullerene in the recognition of COS, H2S, SO2, and CS2 gases (environmental pollution)

We employed density functional theory calculations for evaluating the possible usage of B24N24 fullerene in detecting COS, H2S, CS2, SO2 gases. The interaction stability sequence for the gases under investigation is generally as follows: SO2 > H2S > COS > CS2. Seemingly, there is an association between molecules’ electric dipole moment and absorption energy. B24N24 fullerene as Ф-type sensor for SO2 and CS2 is regarded as an electronic sensor. It is found that CS2 and SO2 can be recognized by B24N24 fullerene at the H2S presence and COS as a Ф-type sensor. Besides, it has the ability of selective operating between SO2 and CS2 as an electronic sensor for changing varying electrical conductivity values when they are present. It is not a function-type or electronic sensor for H2S and COS gases. For desorbing CS2 and SO2 gases from the surface at ambient temperature, The B24N24 fullerene takes advantage of a short recovery time (0.19 s and 0.4 μs). Thus, this fullerene is able to work in a wet environment.

Effects of point vacancy and interstitial H on the carrier activity, separation, and absorption spectrum of ZnO: Li/Na/K

The accurate understanding of Li/Na/K doping and point vacancies in ZnO is difficult. The interstitial H is also neglected in ZnO. In this paper, the generalized gradient approximation plane wave ultrasoft pseudopotential + U method is adopted based on the spin density functional theory to solve the abovementioned problem. The First-principles method is utilized to study the point vacancies and interstitial H on ZnO: Li/Na/K carrier activity, separation, and absorption spectrum. The formation energy of the Zn35MHiO35 (M: Li/Na/K) system is a large positive value regardless of the O- and Zn-rich conditions, indicating the difficulty of Zn35MHiO35 (M: Li/Na/K) system's formation and its poor stability. Compared with the same doping system, the Zn34MHiO36 (M: Li/Na/K) system exhibits smaller formation energy under O-rich conditions and is more stable. The formation energies of different doping systems under O- or Zn-rich conditions are in the following order: Zn35NaHiO35＜Zn35KHiO35＜Zn35LiHiO35. Zn35NaHiO35 and Zn35KHiO35 have negative formation energy and good stability. According to the analysis of the electric dipole moment, effective mass, and absorption spectrum, Zn35NaHiO35 can be separated easily and has the strongest carrier activity, the best absorption spectrum intensity, and the best red shift. These features are relatively advantageous in designing and preparing novel ZnO photocatalysts.

Temperature dependent optical spectroscopy: A study of holmium diphenanthroline nitrate in DMF.

A detailed spectroscopic study of the optical properties of Ho(phen)2(NO3)3 complex is presented. The substance is characterized by UV/Vis spectroscopy, IR - spectroscopy, chemical analysis and X - Ray diffraction. Temperature dependent absorption spectra of Ho(phen)2(NO3)3 in DMF are discussed. A hyperchromic effect at elevated temperatures of the electric dipole absorption transition 5I8→5G6 at 452 nm is observed and a quantitative explanation in the framework of the coth(x) theory of absorption line broadening is suggested. The thermal depopulation of the 5I8 electronic level also is discussed.

Natural anisotropic nanoparticles with a broad absorption spectrum for solar energy harvesting

Optical properties of spherical nanoparticles, made of natural hyperbolic material-Bi2Te3, are studied numerically based on the Mie theory from the ultraviolet to the near-infrared region. The absorption efficiency factor of an anisotropic spherical nanoparticle is calculated by superimposing contributions from different polarizations. The numerical results show that Bi2Te3 nanoparticles exhibit broadband absorption in the wavelength range of 300–2400 nm with several absorption peaks, owing to the simultaneous excitation and superposition of electric and magnetic dipole resonances. In order to elucidate the mechanism of resonance absorption peaks of Bi2Te3 nanoparticles, the Mie theory is used to calculate the electric field inside these nanoparticles by assuming the nanoparticle to be isotropic, having the same dielectric function as either parallel or perpendicular dielectric function of Bi2Te3. It is shown that increasing the size of the Bi2Te3 nanoparticle causes a redshift of the resonance wavelength, an increase in the magnetic dipole absorption peak, and a decrease in the electric dipole absorption peak. The numerical results also show that Bi2Te3 nanoparticles have high absorption efficiency factor in the wavelength of 300–2400 nm, demonstrating their potential to be used for harvesting solar energy.

The Mechanisms of Absorption of Terahertz and Infrared Radiation in PZT Films

Terahertz and IR spectra of dielectric response of dense and porous Pb(Zr,Ti)O3 films deposited on single-crystal magnesia and alumina substrates and on silicon substrates with a conducting platinum sublayer are measured in the and analyzed. We consider the key mechanisms of electric dipole absorption that give rise to absorption bands observed in experimentally measured reflection and transmission spectra, and discuss the relationship between the type of substrate and the parameters characterizing the absorption bands in the spectra of the prepared PZT films.

Механизмы поглощения терагерцового и инфракрасного излучения в пленках PZT

AbstractTerahertz and IR spectra of dielectric response of dense and porous Pb(Zr,Ti)O_3 films deposited on single-crystal magnesia and alumina substrates and on silicon substrates with a conducting platinum sublayer are measured in the and analyzed. We consider the key mechanisms of electric dipole absorption that give rise to absorption bands observed in experimentally measured reflection and transmission spectra, and discuss the relationship between the type of substrate and the parameters characterizing the absorption bands in the spectra of the prepared PZT films.

Electric-dipole absorption resonating with longitudinal optical phonon-plasmon system and its effect on dispersion relations of interface phonon polariton modes in metal/semiconductor-stripe structures

Interface phonon polaritons (IPhPs) in nano-structures excluding metal components are thoroughly investigated because they have lower loss in optical emission or absorption and higher quality factors than surface plasmon polaritons. In previous reports, it is found that strong infrared (IR) absorption is based on the interaction of p-polarized light and materials, and the resonance photon energy highly depends on the structure size and angle of incidence. We report the optical absorption by metal/semiconductor (bulk-GaAs and thin film-AlN)-stripe structures in THz to mid-IR region for the electric field of light perpendicular to the stripes, where both of s- and p-polarized light are absorbed. The absorption resonates with longitudinal optical (LO) phonon or LO phonon-plasmon coupling (LOPC) modes, and thus is independent of the angle of incidence or structure size. This absorption is attributed to the electric dipoles by the optically induced polarization charges at the metal/semiconductor, heterointerfaces, or interfaces of high electron density layers and depression ones. The electric permittivity is modified by the formation of these dipoles. It is found to be indispensable to utilize our form of altered permittivity to explain the experimental dispersion relations of metal/semiconductor-IPhP and SPhP in these samples. This analysis reveals that the IPhPs in the stripe structures of metal/AlN-film on a SiC substrate are highly confined in the AlN film, while the permittivity of the structures of metal/bulk-GaAs is partially affected by the electric-dipoles. The quality factors of the electric-dipole absorption are found to be 42–54 for undoped samples, and the value of 62 is obtained for Al/AlN-IPhP. It is thought that metal-contained structures are not obstacles to mode energy selectivity in phonon energy region of semiconductors.

Local vs Nonlocal States in FeTiO3 Probed with 1s2pRIXS: Implications for Photochemistry.

Metal–metal charge transfer (MMCT) is expected to be the main mechanism that enables the harvesting of solar light by iron–titanium oxides for photocatalysis. We have studied FeTiO3 as a model compound for MMCT with 1s2pRIXS at the Fe K-edge. The high-energy resolution XANES enables distinguishing five pre-edge features. The three first well distinct RIXS features are assigned to electric quadrupole transitions to the localized Fe* 3d states, shifted to lower energy by the 1s core–hole. Crystal field multiplet calculations confirm the speciation of divalent iron. The contribution of electric dipole absorption due to local p-d mixing allowed by the trigonal distortion of the cation site is supported by DFT and CFM calculations. The two other nonlocal features are assigned to electric dipole transitions to excited Fe* 4p states mixed with the neighboring Ti 3d states. The comparison with DFT calculations demonstrates that MMCT in ilmenite is favored by the hybridization between the Fe 4p and delocalized Ti 3d orbitals via the O 2p orbitals.

Pressure broadening of the electric dipole and Raman lines of CO2 by argon: Stringent test of the classical impact theory at different temperatures on a benchmark system

A classical approach is applied to calculate pressure broadening coefficients of CO2 vibration–rotational spectral lines perturbed by Ar. Three types of spectra are examined: electric dipole (infrared) absorption; isotropic and anisotropic Raman Q branches. Simple and explicit formulae of the classical impact theory are used along with exact 3D Hamilton equations for CO2–Ar molecular motion. The calculations utilize vibrationally independent most accurate ab initio potential energy surface (PES) of Hutson et al. expanded in Legendre polynomial series up to lmax = 24. New improved algorithm of classical rotational frequency selection is applied. The dependences of CO2 half-widths on rotational quantum number J up to J=100 are computed for the temperatures between 77 and 765K and compared with available experimental data as well as with the results of fully quantum dynamical calculations performed on the same PES. To make the picture complete, the predictions of two independent variants of the semi-classical Robert-Bonamy formalism for dipole absorption lines are included. This method. however, has demonstrated poor accuracy almost for all temperatures. On the contrary, classical broadening coefficients are in excellent agreement both with measurements and with quantum results at all temperatures. The classical impact theory in its present variant is capable to produce quickly and accurately the pressure broadening coefficients of spectral lines of linear molecules for any J value (including high Js) using full-dimensional ab initio - based PES in the cases where other computational methods are either extremely time consuming (like the quantum close coupling method) or give erroneous results (like semi-classical methods).

Electromagnetic-radiation absorption by a small conducting cylindrical particle with the mechanism of the surface scattering of charge carriers taken into account

The cross section of the electric dipole absorption of a small conducting cylindrical particle located in the field of a plane electromagnetic wave is calculated in terms of the classical kinetic theory of electrical conductivity. The boundary conditions of the nonequilibrium charge-carrier distribution function are specified using the Soffer model taking into account the dependence of the specular reflectance on the surfaceroughness parameter and the angle of electron (hole) incidence on the particle’s internal surface. The results of calculating the cross sections of the electromagnetic-radiation absorption of metal and semiconductor particles are presented. The obtained results are compared with theoretical calculations for the model of diffusespecular Fuchs boundary conditions.

Dielectric absorption of s-polarized infrared light resonant to longitudinal optical phonon energy incident on lateral (0 0 0 1) GaN/Ti stripe structures

The interaction of a semiconductor surface or interface and p-polarized infrared (IR) light has been investigated from the viewpoint of terahertz (THz) application. In this study the electric dipole absorption at the resonant energy to a longitudinal optical (LO) phonon of approximately 22 THz achieved using a lateral GaN/Ti stripe structure and s-polarized light, is clearer than the previously reported weak signal obtained using a film structure and p-polarized light. The previously proposed function of permittivity is validated by the analysis of Raman spectra in addition to IR analysis for the present sample structure. In the Raman spectra an additional peak is found at the higher-energy side of the LO phonon peak. The phonon-induced charges at the lateral GaN/Ti interface are greater than those at film interface, causing a greater dipole moment and stronger absorption in the vicinity of the LO phonon energy.

Relativistic configuration-interaction calculations of electric dipole [formula omitted] transitions for medium-charge Li-like ions

In this work, the multi-configuration Dirac–Fock and relativistic configuration-interaction methods have been used to calculate the transition wavelengths, electric dipole transition probabilities, line strengths, and absorption oscillator strengths for the 2s–3p, 2p–3s, and 2p–3d transitions in Li-like ions with nuclear charge Z=7–30. Our calculated values are in good agreement with previous experimental and theoretical results. We took the contributions from Breit interaction, finite nuclear mass corrections, and quantum electrodynamics corrections to the initial and final levels into account, and also found that the contributions from Breit interaction, self-energy, and vacuum polarization grow fast with increasing nuclear charge for a fixed configuration. The ratio of the velocity to length form of the transition rate (Av/Al) was used to estimate the accuracy of our calculations.

Precision considerations of classical and semiclassical methods used in collision line broadening calculations: Different linear molecules perturbed by argon

The accuracies of the classical and semiclassical methods currently used in collisional spectral line broadening calculations of molecules are compared. The primary goal is to elucidate the validity of each particular method applied to linear molecules that have different rotational constants but which are perturbed by the same atom. Vibration–rotational electric dipole absorption spectra of CO2, C2H2, CO, HCl and HF molecules perturbed by an Ar atom are examined at room temperature. The most accurate vibrationally independent potential energy surfaces (PESs) are applied to all molecular pairs. The following theoretical approaches are involved in cross-examination: two classical schemes (exact C3D and C3Diso) and four semiclassical formalisms (NG—of Neilsen and Gordon, PA—peaking approximation, SGC—of Smith, Giraud and Cooper, and RB—of Robert and Bonamy). Identical “exact” isotropic trajectories, driven by only the isotropic part of the PES, are used in C3Diso and in all semiclassical calculations. The comparison is made with experimental data as well as with benchmark quantum dynamical results obtained in the same conditions within close coupling and coupled states schemes. Quantum results reproduced the experimental data excellently in all cases considered, which is as it should be if the interaction PES is accurate. An exact classical C3D approach displays good results for all molecules. By contrast, NG, PA and SGC semiclassical formalisms seriously underestimate line broadening for molecules with small rotational constants (CO2, C2H2 and, to a lesser extent, CO), mainly due to the use of isotropic trajectories in these schemes. The RB method strongly overestimates line broadening for the majority of values of the rotational quantum number J for all molecules studied. The only exception is the case of HF molecules at high J values, where PA, SGC and RB semiclassical schemes provide good results, coinciding well with quantum CC calculations for J>3. Mean overall magnitudes of relative errors, taking an average over all J values and all five molecules studied and of the methods considered are C3D—11%, C3Diso—14%, NG—14%, PA—12%, SGC—14% and RB—21%.

Microwave absorption in powders of small conducting particles for heating applications

In microwave chemistry there is a common misconception that small, highly conducting particles heat profusely when placed in a large microwave electric field. However, this is not the case; with the simple physical explanation that the electric field (which drives the heating) within a highly conducting particle is highly screened. Instead, it is the magnetic absorption associated with induction that accounts for the large experimental heating rates observed for small metal particles. We present simple principles for the effective heating of particles in microwave fields from calculations of electric and magnetic dipole absorptions for a range of practical values of particle size and conductivity. For highly conducting particles, magnetic absorption dominates electric absorption over a wide range of particle radii, with an optimum absorption set by the ratio of mean particle radius a to the skin depth δ (specifically, by the condition a = 2.41δ). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately σ ≈ 3ωε(0) ≈ 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples.

Possible origin of the anomalous far-infrared absorption by small metal particles

We carried out the far-infrared transmission measurements on the ligand stabilized Au55 particles dispersed in CsI. We found that the far-infrared absorption coefficient recovers the ω2-dependence (the same behavior as the classical electric dipole-like absorption) for frequencies above the crossover energy Ec=ℏ2/2mea2∼160cm−1 (a=particle radius) while the absorption coefficient below Ec, which arises from the transitions of the electrons between the discrete energy levels, saturates to a value ∼4cm−1 at ω∼Ec. Since Ec of the small metal particles (a>20Å) studied in the past falls well below the lowest frequency typically accessible for the far-infrared spectroscopy (ω∼20cm−1), we conclude that all the previously measured far-infrared absorption must have been an extension of the absorption of the quantum regime set at Ec, making the absorption measured in the typical far-IR window (20cm−1<ω<120cm−1) anomalously large when compared with the classical electric dipole absorption by the same size particles.

Relativistic configuration interaction calculations on Kα X-ray satellites of magnesium ions

In this work, the multi-configuration Dirac-Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used to calculate the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα X-ray from Mg III to Mg XI. We also take the contributions from the Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels, into account. The present values for Mg X and Mg XI were in good agreement with the previous experimental and theoretical results. The new data in this work provide reference values for the level lifetimes, charge state distributions, and average charge of magnesium plasmas.

Relativistic configuration interaction calculations on Kα x-ray satellites of krypton

The multi-configuration Dirac–Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used for computing the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα x-rays from Kr XXVII to Kr XXXV. The contributions from Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels have been taken into account. The calculated values showed good agreement between these results and recent theoretical and experimental results. These data provide reference values for the level lifetimes, charge state distribution and average charge of krypton plasmas.

Atomic Theory of Parity-Odd (E1–M1) Photon Absorption Event

Light scattering proceeding through electric and magnetic dipole absorption events (E1–M1) exhibits natural circular dichroism, widely used in the characterization of chiral media, and the magneto-chiral effect, which is under consideration as a mechanism for the homo-chirality of life. Additional manifestations of E1–M1 scattering are resonance enhanced Bragg diffraction and non-reciprocal linear dichroism. In spite of its established importance for a raft of significant phenomena, there has not been a complete treatment of E1–M1 light scattering by electrons. Starting from the interaction that includes both electron spin and angular momentum variables, we construct scattering that proceeds via a spin–orbit split intermediate state for the photo-ejected electron. Employing new relations for re-coupling angular momentum we give a theoretical basis for the derivation of sum-rules for integrated dichroic signals. In order to assist in the interpretation of the algebraic terms present for E1–M1 we construct ...

Excitation of Si2O molecule under external electric field

The present work is devoted to the study of the excitation of two kinds of Si2O isomers. The results show that the is excitation energies, oscillator strengths, transition electric dipole moments and absorption spectra are affected evidently by external electric field. The triangular Si2O(C2v,1A1) has no visible light absorption spectrum under no external electric field, however, it has faint absorption spectrum(407.18—526.93 nm) in the visible region under external electric field. The linear Si-Si-O(C∞v,3Σ-) has absorption spectra in blue light region and in purple light both in the presence and in the absence of external electric field. One of the important results is that the linear Si-Si-O has strong blue light absorption spectrum(478.88—488.59 nm).